During the past year there has been an expansion of the HLA matched donor pool and increased use of autologous frozen platelets. One can predict the long-term platelet alloimmunization status of patients with acute nonlymphocytic leukemia by the end of induction therapy. With few exceptions patients who do not develop lymphocytotoxic antibodies within six to eight weeks of platelet transfusion never subsequently developed antibodies despite subsequent transfusions. A randomized study comparing the rate of alloimmunization in patients receiving lymphocyte depleted and standard platelet concentrates is in progress. Platelet cryopreservation using glycerol-glycose produces inferior results to platelets frozen with DMSO in vitro and in vivo. Platelets stored in the presence of Amberlite resin which serves to preserve higher ambient pH's can maintain morphologic integrity and ATP levels compared to platelets stored for long periods of time at ambient temperature without the resin. Nonmatched 111 Indium labeled granulocytes do not migrate to sites of infection in alloimmunized patients and in vitro techniques which may be suitable as a crossmatch are being studied.